In modern audio devices, in particular audio devices intended for installation in motor vehicles, one strives to form as many elements of the device as possible as integrated circuits in order to obtain a cheap and compact structure of the device with high efficiency at the same time. Audio devices for motor vehicles consist in the simplest case of only a radio; more modern components additionally have a cassette section. Devices developed more recently contain a compact disk device in addition to the radio.
The signals from the tuner section of the radio, the cassette or the compact disk device are processed further in modern audio signal processors with the aid of just one integrated circuit before being supplied to the power output stage. Such an audio signal processor contains an AM/FM stereo decoder section, filters for selectively attenuating high, middle and low frequencies, a switchover part for switching over to mono operation if the received field strength is too low for stereo operation, and further circuit parts. The individual elements of the audio processor are almost completely controlled digitally.